In the fields of waste processing, food preparation, scrap metal processing, pulp and paper manufacturing etc., a common challenge is to separate relatively soft or flowable material from relatively rigid hard residual material.
In metal processing for example, chips, shavings and other scrap metal are often produced contaminated by cutting oil. This contamination greatly reduces the price paid for such scrap due to the added steps required in removing oil prior to reuse of the metal. Conventional devices merely compress such scrap into compact cubes or cylindrical briquettes to reduce the bulk of shipping, however no prior art metal scrap densifying device recognizes the improvement in profitability that could result from a reduction in the oil content.
In pulp and paper manufacturing, fibrous pulp material is separated from water that is used in processing, bleaching, and conveying pulp. The incomplete removal of all fibrous material constitutes a water contamination problem and wastes fibers that could be utilized if recovered.
For example, U.S. Pat. No. 4,036,359 to Strictland describes a method of dewatering wood chips to form cube shaped compact bales by squeezing the chips with hydraulic rams in a compression chamber having perforated walls. U.S. Pat. No. 4,287,823 to Thompson describes a wood pulp baler and dewatering device that recovers pulp fibers by a similar straining process under pressure.
Such devices succeed in separating liquid from solid, however, the relatively low pressures which are used for soft wood chips and fibers are not sufficient to extract oil from scrap metal chips for example, or other high strength materials.
In waste processing, waste packaged foods are more efficiently disposed of when separated into waste food, which can be reprocessed into animal feed, and waste packaging, which can be recycled. Since the metal cans used for packaging constitute valuable scrap metal, the prior art waste processing devices have proposed recovery methods. For example, U.S. Pat. No. 5,230,917 to Peters describes lacerating cans, spraying with water to rinse away and reclaim the food and recovering the metal with a magnetic separator. This method results in a rather large expensive and complex machine that does not appear to be justifiable except where the volume of waste is very large. In most applications, disposal of waste in landfill dumps would likely remain the most economical choice.
In food processing, several applications require separation of materials. For example, in U.S. Pat. No. 4,230,733 to Tilby juice is extracted by applying axial pressure to pulp in a cylindrical chamber with an end screen, and in U.S. Pat. No. 4,536,920 to Amersfoort a filtering arrangement is used to extrude meat paste separating it from bone.
Again, in food processing, the pressures required fall far short of what is required to separate relatively high strength materials such as metal cans and food, or metal scrap and oil. The design of the straining or filtering screens and supporting structures clearly do not contemplate high pressure operation and are thereby severely limited in scope.
It is desirable therefore to produce a device that can separate a composite raw material into constituent flowable and residual materials, but at extremely high pressures. Operation at high pressures allows application of such a device to wastes and processes that are inadequately addressed by complex or ineffective prior art methods.